The Mw 7.4 17 August 1999 I??zmit earthquake ruptured five major fault segments of the dextral North Anatolian Fault Zone. The 26-km-long, N86??W - trending Sakarya fault segment (SFS) extends from the Sapanca releasing step-over in the west to near the town of Akyaz?? in the east. The SFS emerges from Lake Sapanca as two distinct fault traces that rejoin to traverse the Adapazar?? Plain to Akyaz??. Offsets were measured across 88 cultural and natural features that cross the fault, such as roads, cornfield rows, rows of trees, walls, rails, field margins, ditches, vehicle ruts, a dike, and ground cracks. The maximum displacement observed for the I??zmit earthquake (???5.1 m) was encountered on this segment. Dextral displacement for the SFS rises from less than 1 m at Lake Sapanca to greater than 5 m near Arifiye, only 3 km away. Average slip decreases uniformly to the east from Arifiye until the fault steps left from Sagir to Kazanc?? to the N75??W, 6-km-long Akyaz?? strand, where slip drops to less than 1 m. The Akyaz?? strand passes eastward into the Akyaz?? Bend, which consists of a high-angle bend (18??-29??) between the Sakarya and Karadere fault segments, a 6-km gap in surface rupture, and high aftershock energy release. Complex structural geometries exist between the I??zmit, Du??zce, and 1967 Mudurnu fault segments that have arrested surface ruptures on timescales ranging from 30 sec to 88 days to 32 yr. The largest of these step-overs may have acted as a rupture segmentation boundary in previous earthquake cycles.
Additional Publication Details
Geometry, slip distribution, and kinematics of surface rupture on the Sakarya fault segment during the 17 August 1999 I??zmit, Turkey, earthquake